Pump



July 13, 1965 H. scHoTTLER 3,194,172

PUMP

Filed April 19. 1962 8 Sheets-Sheet 1 July 13, 1965 H. scHoTTLER 3,194,172

PUMP

Filed April 19, 1962 8 Sheets-Sheet 2 INVENTOR.

July 13, 1965 H, SCHQTTLER 3,194,172.

PUMP

Filed April 19, 1962 8 Sheets-Sheet yI5 INVEN TOR.

July 13, 1965 H. scHoTTLER PUMP 8 Sheets-Sheet 5 Filed April 19, 1962 www NNN wv@ NNN www Q July 13, 1965 H. scHoTrLl-:R

v PUMP 8 Sheets-Sheet 6 Filed April 19, 1962 July 13, 1965 H. SCHOTTLER 3,194,172

PUMP

Filed April 19, 1962 8 Sheets-Sheet '7 {lll/U///////////l7///////////////////// IN VENTOR.

July 13, 1965 H. scHo'rTLER PUMP United States Patent O 3,194,172 PUMP Henry Schottler, 8MS Country Club Lane, North Riverside, Ill. Filed Apr. I9, 1962, Ser. No. 188,777 16 Claims. (Cl. 10S-162) This invention relates to a fluid device and more particularly to a swash plate type iluid pump or motor. The invention further relates to an improved control for the fluid device. l

In swash plate type fluid pumps and motors large thrust forces are created between the swash plate assembly and the cylinder block assembly as a result of the reciprocation of the pistons. Heretofore these thrust forces have ordinarily been transferred from the rotating parts to the casing through thrust bearings. It is well known, however, that thrust bearings involve considerably higher friction losses than are encountered in ordinary radial type anti-friction bearings, particularly at relatively high speeds of rotation. Furthermore, thrust bearings are somewhat more expensive to manufacture and are subject to a higher rate of wear. Prior to the present invention, however, there has been no practical way of avoiding their use.

To avoidrallV of these problems the swash plate hydraulic devices of the present invention embody an entirely new concept in which thrust forces are self-contained in the rotating parts so that ordinary radial bearings may be utilized to rotatably mount the swash plate assembly and the cylinder block assembly.

Swash plate devices in the past have also ordinarily utilized universal joints in order to synchronize the speed of rotation of the swash plate and the cylinder block while rotating with their axes at an angle. Earlier devices utilized standard universal joints of the Hookes or Cardan type which did not transmit uniform or constant velocity drive between the swash plate assembly and the cylinder block assembly, and such non-constant `velocity universal joints are still utilized in some swash plate devices employing relatively low speeds. However, in swash plate devices operating at relatively high speeds it has been imperative to utilize so-called constant velocity universal joints which transmit true constant velocity between the rotating members, or at least a velocity approaching true constant velocity. Otherwise the periodic liuctuations in speed result in high frequency vibrations causing early failure. Furthermore, as the angularity between the shafts is increased the speed fluctuations increase with the square of the change in angle, resulting in much more serious problems at higher angles. Constant velocity universal joints which solve the vibrational problems are expensive and far from foolproof. Furthermore, they introduce a serious installation problem and ordinarily increase the space requirements. By reason of the novel construction of the swash plate devices of the present invention, no universal joint at all is required between the swash plate assembly and the cylinder block assembly, thus completely eliminating all of these problems.

It is an object of the present invention to provide an improved Huid device of the swash plate type.

. An important object is to provide an improved swash plate fluid device without a universal joint between the swash plate assembly and the cylinder block assembly.

An additional important object is to provide a swash plate fluid device utilizing radial bearings only.

Another object of the invention is to provide a swash plate pump or motor which does not require either a universal joint or thrust bearings.

A further object of the present invention is to provide ceN a swash plate device wherein the thrust. load between the swash plate assembly and the cylinder block assembly is self-contained.

Still another object is to provide a swash plate device having a thrust member rotating with the swash plate :assembly and the cylinder block assembly to directly transmit the thrust load therebetween.

A still further object of the invention is to provide a swash plate type pump or motor having a thrust mem-` ber which cooperates with the swash plate assembly to transmit the thrust load on said swash plate assembly back to the cylinder block assembly, wherein said swash plate and said thrust memberare separated from one another by an oil lm automatically maintained at a predetermined thickness.

It is an additional object of the present invention to provide a swash plate device having a self-centering port plate which minimizes shear and leakage losses within said pump.

Another object is to provide a swash plate type pump or motor wherein `the pistons are positively actuated by the relative movement between the cylinder block assembly and the swash plate assembly.

A further object of the present invention is to provide an improved control device wherein a control member may be rotated automatically through a predetermined arc.

Still another object of the invention is to provide a fluid actuated control system wherein a shaft, pinion or the like may be automatically rotated through an arc determinded by the rotation of a control knob.

Other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGURE l is a longitudinal sectional view with parts in elevation, of a swash plate pump embodying the features of the present invention; .t

FIGURE 2 is a sectional view of the pump of FIGURE 1 taken along line 2 2 of FIGURE l;

FIGURE 3 is a sectional View taken along line 3 3 of FIGURE l;

FIGURE 4 is a sectional view taken along line 4-4 of FIGURE l;

FIGURE 5 is a sectional View taken along line 5-5 of FIGURE l;

FIGURE 6 is a sectional view taken along line 6-6 of FIGURE 1;

FIGURE 7 is a sectional view taken along line 7-7 of FIGURE 1;

FIGURE 8 is a graphical illustration showing the effect upon shear and leakage losses when the port plate of the pump of FIG. 1 is out of center;

FIGURE 9 is a longitudinal sectional view of a modied swash plate pump embodying the features of the present mvention;

FIGURE l0 is a sectional View taken along line 11)-10 of FIGURE 9;

FIGURE l1 is a sectional view taken along line 11-11 of FIGURE 9;

FIGURE l2 is a sectional view taken along line i12-12l of FIGURE 9;

FIGURE 13 is a` sectional viewtaken along line 13a-13 of FIGURE 9;

FIGURE 14 is a fragmentary sectional view of a` swash plate pump embodying a modified construction wherein the swashplate assembly is coupled to the pistons in the FIGURE 16 is a fragmentary sectional view of the the axis 64 and integral with the swash plate Se.

control system of the present invention adapted in this instance lto change the position of this axis of the swash Y plate assembly;

' 1. The .FIGURE 1-8 pump Referring now to FIGURES 1 8, a swash plate pump embodying features of the present invention is indicated generally by reference numeral 3i). The pump 30 may be employed as a motor but herein will be described in connection with its pump function.

As seen in FIGURE 1, the pump 3l? includes a stationary housing or casing 32 having open ends, one of which is closed by a cover 34 suitably secured to the casing 32 by nuts and bolts or the like (not shown).

Rotatably supported within the housing 32 on antifriction radial type ball bearings 36 and 38 is a swash plate type pump mechanism, indicated generally by reference numeral 49. The pump mechanism 4t) includes a cylinder block assembly 42, a thrust member 44 and a swash plate assembly 46. The cylinder block assembly 42 is rotatably mounted in the casing through the antifriction bearing 36, and the thrust member is rotatably mounted through the anti-friction bearing 33. The axis of rotation of the pump mechanism 4@ is the axis of the cylinder block assembly 42 and thevthrust member 44 and is indicated generally by reference numeral 82.

The thrust member 44 is generally bell-shaped with open ends 52 and 54. The cylinder block assembly 42 extends into the open end 52 and is secured to the thrust member 44 by a snap ling 48 or the like. In this manner the thrust member 44 and the cylinder block assembly 42 rotate together. The thrust member 44 has a concave segmental spherical surface t) which cooperates with the swash plate assembly 46 in a manner discussed in more detail hereinafter.

The swash plate assembly 46 includes a swash portion or plate 56 with an integral, axially aligned shaft 58. The shaft 58 extends through the open end 54 of the thrust member 44, and has its free end rotatably supported in an anti-friction roller bearing assembly 66. The swash plate 56 has an annular, conically shaped swash face 62 concentrically positioned about an axis 64 of the swash platey assembly 46 and facing toward the cylinder block assembly 42. Also extending toward the cylinder block assembly 42 is a cylindrical projection 65 coaxial with A free end of the projection 65 has a segmental spherical socket 66, coaxial with the axis 64 of the swash plate assembly 46, which opens toward the cylinder block assembly 42.

' Extending axially through the dispenser 68 is a passageway 69 which communicates with the chamber 67.

Also communicating with the chamber 67 is an axially extending passageway 76 in the swash plate 56 which branches out into radially extending passageways 72 communicating with an annular groove 74 formed between annular lands 76 and 78 on the exterior surface of the swash plate 55. Segmental spherical surfaces 80 of the lands 76 and 78 deline a segmental sphere having a diameter substantially equal to the diameter of the concave segmental spherical surface 5t) of the thrust member 44. Accordingly, the swash plate assembly 46 is universally tiltably associated with the thrust member 44.

The swash plate assembly 46 is tiltable by moving its axis 64 in a tilt or swash plane 93 (see FIGURE 2).

The axis of rotation $2 lies in this plane 93. The tilting is effected by moving the free end of the shaft 53 which is supported in the radial roller bearing et). The angle between the axis 64 of the swash plate assembly 46 and the axis of rotation S2 is referred to as the swash angle and is designated by A. It will be seen that when the swash angle A is zero the axis 64 of the swash plate assembly and the axis of rotation 82 coincide.

As seen in FIGURES 1 and 2, the roller bearing assembly eil is secured by a press fit or other suitable means within a non-rotatable guide member S4 having an external rack Se thereon which meshes with a rotatable pinion S8. The cover 34 has two opposing parallel internal guide iiats 99, which are parallel to the tilt plane 93. These cooperate with two complementary flats 92V on the guide member S4 whereby rotation of the pinion 88 moves the guide member 84 parallel to the guide liats 9i) to increase or decrease the swash angle A on either side of the axis of rotation $2. In this manner, the swash Vplate assembly 4u may be tilted to control the capacity and flow direction of the pump Sil.

As seen in FIGURES 1 and 3, the cylinder block assembly 42 includes a cylinder block 94 having a plurality of cylinders 9S therein, each cylinder 93 containing a reciprocable piston 96. The pistons 96 have convex, spherical heads 96a which cooperate with the swash face 62 of the i swash plate 56. The face e2 normally contacts the heads r cordingly, the pumpy displacement, increasing with increased swash angle. Oil to be pumped enters each cylinder 9S as its associated piston 96 moves away from the port 102, and the oil is discharged under pressure from the cylinder 93 `as its associated piston 96 moves toward the port 102.

It is preferred, as shown in FIGURE l, to have the axes of the pistons 96 and cylinders 98 lie in a conical plane, since this configuration allows the largest pump capacity with the smallest cylinder block 94. However, it will be understood that the axes of the pistons 96 and the cylinders 9d may be parallel to the axis of rotation 82 or in any other suitable conguration without departing from the spirit of this invention.

Though the pump 3@ of the present invention has been illustrated with nine pistons 96, it will be understood that any number of pistons may be employed. It is preferable, however, to employ an odd number of equally spaced pistons 96.

For rotating the cylinder block assembly 42, the thrust member 44 and the swash plate assembly 46, an externally splined'drive shaft N4 extends through an axial aperture 106 in the housing 32. The axially inward end portion 198 of the drive shaft is secured to the cylinder block 94 through external splines 198er of the shaft which mate with internal splines Il@ formed in an axial hole IIZ of the block 94. Axial movement of the block 94 is prevented by a spring washer Ile and a nut 114, the latter threadedly engaging the inner end portion IS of the shaft 194. i Y

The drive shaft 1534 has an axial passageway 1118 extending from the inner end portion 10S. The axial passageway IIS has an axially inward bore section 129 of enlarged diameter. In fluid-tight engagement with the bore section and axially movable therein is a cylindrical positioning member 124. A spring 122 in the bore section 120 acts upon oneend of the positioning member i714 to urge its other end into abutting relation-V ship with the fluid dispenser 63. p

An axially extending passageway through the position- 45 ing member 124 has secured therein by a press fit or the like a fluid transfer member 126 having a narrow longitudinally extending groove thereon which forms with the positioning member 124 a capillary passageway 128 through which a controlled amount of fluid may flow from the port plate 100 to the annular groove 74 between the surface 50 and the surfaces 80 in a manner more apparent hereinafter. end of the uid transfer member 126 is spaced sufficiently inwardly from the outer end of the positioning member 124 to assure that the capillary passageway 128 will communicate with the passageway 69 in the fluid dispenser 63 despite transverse movement of the fluid dispenser 68.

Also splined or keyed to the drive shaft 104, between an annular ridge 130 on the drive shaft 104 and the nut 114, is a rotating plate 132. An annular spacer 134 is positioned between the plate 132 and the block 94. The plate 132, the spacer 134, and the block 94 are always retained in this abutting relationship by the spring washer 116 and the nut 114 and rotate at the same speed as the shaft 104. The spacer 134 has a slightly larger longitudinal dimension, in the order of `about .001 inch, than the non-rotatable port plate 100 to effect the self-centering feature of the port plate 100 to be discussed in more detail hereinafter.

The port plate 100 is non-rotatably secured to the housing 32 by a set screw 135 (see FIG. 5) which cooperates with a longitudinal slot 137 in the periphery of the port plate 100. In this manner, the port plate 100 is free to move axially substantially the length of the slot 137. Two annular grooves 136 on opposite ends of the slot `137 extend around the periphery of the port plate 100 and form passageways with the housing 32 (see FIGS. l and 4-6). longitudinally extending, diametricaiiy opposing seals 133 in the tilt plane 93 prevent yoil from flowing through the grooves 136 across the seals 138. The plane 93 is the division between the high pressure side and the low pressure side of the port plate 100, and the seals 13S minimize circumferential oil flow around the port plate 100 from the high pressure side tothe low pressure side. i

The port plate 100 has an annular land 140 at one end which is slidably associated with a complementary annular land 142 of the cylinder block 94. Two kidneyshaped ports 144:1 and 146e in the land 140 communicate with channels 144 and 146, respectively, in the port plate 100. These channels 144 and 146 communicate with openings 148 and 150, respectively, in the housing 32. The tilt plane 93 in which the axis 64 of the swash plate assembly 46 is tilted bisects the port plate 100 and divides it into two semi-circular sections, with the kidney ports 144:1 and 146:: symmetrically disposed in these two half-sections of the port plate 100. The adjacent ends of the kidney ports 144:1 and 146e are spaced suihciently far apart that one cylinder port 102 may not communicate with both the kidney ports 144e and 146:1 at the same time.

`cylindrical projections 152 and 154, respectively, (see FIGS. 1, 4 and 5) which do not extend past the outer periphery `of the port plate 100. Radially extending passageways 156 and 158 extend through the projections 152 and 154, respectively, `and communicate with the channel 144 and the kidney port 144:1 and the channel `146 and the kidney port 146e, respectively. Each passageway 156 and 158 has therein a one-Way check valve 1st) and 162, respectively, which permits oil Ito flow through its respective passageway in only one direction.

As shown in FIGURE l, the outer i As illustrated in FIGURE 5, the one-way check valves 160 and 162 are spring-biased ball valves, but it will be understood that any suitable type of one-way check valve may be employed. The check valves 160and 162 are set in opposing relationship, that is, in such a manner that oil may flow to the right (when viewing FIG. 5) through the passageway 156 but may not ow to the left through the passageway 156. By contrast, the valve`162 allows fluid to flow through the passageway 15S from right to` left (when viewing FIG. 5) but not from left to right.

The spacer 134 has `two coaxial radially extending holes 166 and 168 (see FIGS. 1 and 5) extending therethrough which communicate with an annular groove 164 in the `outer periphery of the spacer. The groove 164 communicates with the passageways 156 and 158. Similarly,` the drive shaft 104 has a radially extending passageway 170 extending therethrough which communicates with the axially extending passageway 118 and an annular groove 172 in the periphery of the shaft 104. The groove 172 communicateswith the passageways 166 and 168 in the spacer 134. i i

Two cylindricalmembers 174 and 176 having narrow grooves 174e and 176:1, respectively, are press tted :into bores in the port plate 100. These grooves form capillary passageways which communicate with the channels 144 and 146, repsectively, and with kidney-shaped relief ports and 182, respectively, formed in a land 184 at the `opposite end of the port plate 100. As seen in FIGURE 6, these relief ports 180 and 182 are axially aligned with and have the same cross-sectional dimensions as the kidney ports 146:1 and 144:1, respectively.

A face 105 of the plate 132, which is slidably asso` ciated with the land 134 -of the port plate 100, has relief ports 137 therein (see FIG. 7). There are the same number of relief ports 187 as there are cylinder ports 102. The ports 1%7 and 102 have the same transverse crosssectional dimensions and each cylinder port 102 has an opposed, axially aligned port 187.` The alignment between the plate 132, the port plate 100 and the cylinder block 94 is maintained` during operation inasmuch as they are mounted for concurrent rotation with the drive shaft 104 in the manner discussed hereinbefore..`

11. operation 0f the FIGURE 1 8 pump In discussing the operation of the pump 30, it will be assumed that the-drive shaft 104 rotates in the direction indicated by the arrow in FIGURE 1 and that the swash angle A between the axis 64 of the swash plate assembly 46 and the axis of rotation S2 is greater than 0 in the direction shown in FGURE 1. When the pump 30 is actuated by rotation of the drive shaft 104, the plate 132, the spacer 134, the cylinder block assembly 42 and the thrust member 44 rotate in the `same direction and at the `same speed as the drive shaft 104. Through the contact of the swash face 62 of the swash plate 56 upon the pistons 96 and through the force exerted by the positioning member 124 upon the iiuid dispenser 68, theswash plate assembly 46 will also rotate in the same direction as the other membens and at substantially the same speed. However, it is not imperative that the swash` plate `assembly 46 rotate at the same speed as the cylinder block assembly 42 or the thrust member 44.

During the rotation of the cylinder block assembly 42, half of the pistons 96 will be moving toward theirrespective cylinder ports 102, i.e., in their compression strokes, while the other pistons 96 will be moving away from their respective channel 102, i.e., in their intake strokes, except `when individual pistons are bottom dead center position venters the opening 150 of the housing 32 and passes through the channel 146 and the kidney port Moa into the piston chambers 98 via the cylinder ports 102 communicating with the kidney port 146o. As the piston 96 reaches bottom dead center position its port 102 is blocked by the land 140 and will no longer communicate with the kidney port lada.

As the cylinder block assembly 42 continues rotation, the piston h6 then begins its compression stroke because of its cooperation with the swash face 62 of the swash plate 56. Simultaneously therewith the cylinder port 102 communicates with the kidney port 14451. In this manner,y as the piston 96 moves toward top dead center position, fluid is being compressed in the piston chamber 9S and forced out through the cylinder port 1h12 into the kidney port'ldda and the channel 1li-4 and out of the housing 32 through the opening 143.

As the piston 96 completes its compression stroke, i.e., it reaches top dead-center position, the land 1d() again blocks oif channel 102. The cycle is repeated as the piston 96 begins its intake stroke and simultaneously its piston chamber 98 communicates with the kidney port 14de.

It will be understood that if the swash angle A is decrea-sed, the capacity of the pump 3@ is decreased as the piston 96 goes through a shorter intake and compression stroke. Therefore, -it will be understood that when the swash angle A is no pumping action is effected by the pump Sil. The pump 3i) is then in its neutral position.

If the shaft 104 is rotated in the opposite direction, then the opening 148 becomes the inlet for the oil and Vthe opening 15h becomes the pump outlet. The operation of thepurnptl is identical to that described hereinbefore with the exception that the intake and pressure sides of the pump 3i) have therefore been reversed.

Likewise the pump 3@ may be reversed by actuation of the pinion 88 to change the swash angle A such that it is on the other side of the axis of rotation 82.

Thrust, of course, is created during the operation of the pump 30. According to this invention, the thrust is transmitted from the pistons 96 to the swash plate assembly ed, but instead of being transmitted from the swash plate to the casing through a thrust bearing, the thrust force exerted against the thrust member 44 is carried back to the cylinder block 94. Furthermore, by this arrangement the need for a universal joint has been eliminated. In particular, the thrust force is transferred from the swash plate assembly 46 to the thrust member 44 through the cooperation of the convex surfaces 89 of the lands '76 and 78 with the concave surface 5u of the thrust member. Tol prevent the surfaces d@ and the surface 50 from binding, the pump 3i) is adapted to provide a lubricating film 'of oil of predetermined thickness between the surfaces 8) `and the surface 5b. The film of oil is thick enough to provide adequate lubrication between the surfaces 8% and 50 and yet is thin enough to prevent excessive leakage loss of pressurized oil.

During operation of the pump 3) high pressure oil in the channel 144 will flow through the check valve 160 into the passageway 156. The oil ows through the annular groove 164, the radial passageways 166, the annular groove 172 and the passageway 17th into the axially extend-ing passageway 118 of the shaft 1M. Flowing into the bore action 126 the oil then passes through the capillary passageway 128, the axial hole 69 in the fluid dispenser dand the passageway 70 in the sw-ash plate 56. The oil is distribut-ed by the radially extending passageway 72 to the groove 74 between the lands 7e Vand 73 and lubricate-s the cooperating surfaces Sil and the surface 5t) of the thrust member 4A.

The thrust force exerted by the swash plate assembly 46 upon the thrust member 44 will be substantially equal draait/.e

to the force exerted by the pistons 96 on the swash face 62. This force yis equal to the sum of the forces exerted by each piston 96. Each piston 96 will exert 4a force equal to its cross-sectional area times the pressure of the oil in its respective piston chamber 98. This thrust force must be balanced by the force of the oil lm between the convex surfaces Sti and the concave surface 5t?, Vwhich is equal to the mean pressure of the oil film between the surface 5t? and the surfaces t? times the area of the surfaces 80.

The thrust force of the pistons 96 on the swash face o2 may readily be calculated for a given pump pressure output. Likewise, the desired -oil thickness between the surfaces St) and the surface 5@ may be calculated. Once these have been determined, the desired mean pressure of the oil hlm between the surface 51B and the surfaces t) and the pressure of the oil in the groove 74 may be calculated. Since the pressure of the oil in the passageway 118 and bore section 12th is known, the desired pressure drop across the capillary passageway 12S may be calculated. The size and length of the capillary passageway 12S is constructed accordingly. Thus, during operation of the pump 31th oil is supplied at a sufficient pressure to maintain an oil lm of predetermined thickness between the surfaces 8@ and the surface 5t).

Should the thrust force increase sufficiently to move the surfaces S@ closer to the surface S@ of the thrust member 4d than desired, the flow of oil between the surfaces S@ and the surface 5t) will, of course, be decreased. The resultant reduced flow of oil in the capillary passageways 128 will decrease the pressure drop through the passageway 128, whereby the pressure of the oil between the surfaces 8@ and the face 54B increases and moves the swash plate assembly t6 and the thrust member 44 back to their predetermined distance apart. Likewise, should the thrust force decrease and the surfaces Sti move away from the surface 55B, the flow of oil therebetween will increase. This increase in oil flow will also occur in the passageway 128,-which will increase the pressure drop through the passageway 12E, thereby decreasing the pressure of the oil between the surfaces St) and the surface 5t). This causes the surfaces titl to move closer to the surface Sil -and therefore back to their predetermined spaced relationship. In this manner a predetermined spaced relationship between the surfaces 3@ andthe surface Sil is automatically maintained.

It will be understood that this self-positioning -aspect of the pump 3? operates at any pressure output of the pump 3d, as the pressure drop across the capillary passageway 128 will be a predetermined percentage of the `pressure output which is in the passageway 12%. Furthermore, it will be understood that oil from the channel 144 will enter the passageway 15%, but will be prevented from entering the channel 146 by the check Valve 162.

If the flow of the pump 3@ is reversed by the methods described hereinbefore whereby channel 144- will be carrying the high pressure oil, the operation of the pump 30 is basically the same. However, in such an instance the oil to be supplied to the surfaces 3f@ and the surface 5@ comes from the channel 145 and the passageway 153 through the check valve 162. The check valve 16@ prevents the oil, in this instance, from flowing through to the channel 144.

To reduce shear losses and leakage between the port plate and the plate 132 and the cylinder block 94, the port plate ltlil is adapted to automatically center itself between th-e plate 132 and the cylinder block 94. A small amount of oil will tend to leak between the face M2 of the cylinder block 94 and the face of the'land 140 of the port plate 100 and exert a force upon the port plate 1M toward the left when viewing FIGURE 1. Basically, the self-centering feature of the port plate 1th? is achieved by allowing a controlled amount of oil to flow between the port plate 100 and the rotating plate 132 to create a sufficient force on the port plate 1G@ toward the right to counterbalance these forces acting upon it toward the left.

To these ends, the face 185 of the port plate 100 has a greater surface area than the surface area of the face of the land 14). The kidney ports 14451, 146a, 180 and 182 are, however, `the same size and aligned in the manner `described hereinbefore. The counterbalancing oil llows from the channels 144 and 146 through the grooves 174e and 17651, respectively, to the kidney ports 182 and 180, respectively. The grooves 174e and 176s, provide predetermined pressure drops for the oil passing between the plate 132 and the port plate 100. Since the area of `the face 184 is larger than the area of the face of the land 14d, the pressure of the oil I011 the lett side of the port plate 100 need not be as large as the pressure on the right side of the port plate 101i to exert the same force toward the right as is being exerted toward the left on the port plate i). In this manner the forces on either `side of the port plate 100 are balanced and it is thereby centered between the plate 132 and the cylinder block 94.

If the port plate 100 should move off center toward the right, the land 141) and the face 142 will move together and the faces 185 ond 184 will move apart. As a result, the ow of oil betwen the faces 184 and 185 will increase and likewise the llow of oil through the capillary grooves `is centered between the plate 132 and the block 94 and the forces on either side are balanced.

The reverse occurs if the port plate 100 moves offcenter to the left. In this instance, the iiow of oil between the faces 134 and 185 is reduced. This causes the How of lluid through the capillary grooves 174a and 176a to likewise decrease whereby the pressure drop across these grooves is also reduced. As a result, the pressure of the oil between the faces 184 and 18S increases, thereby increasing the rightward force upon the port plate lill! and causing it to move to the right until it is centered and the forces on both sides of the plate 19t) are balanced.

FIGURE 8 is a graph illustrating the eiect upon shear and oil leakage losses when the port plate 100 is not centered. It will be understood that this is an empirical analysis in which X represents the maximum distance the port plate 1d@ may be oilcenter, i;e., when one face of the port plate 1li@ is in cont-act with the cylinder block 94 or the plate 132, and l represents the centered position of the port plate 1410, i.e., when it is equidistant between the plate 132 and the cylinder block 94.

The graph of FIGURE 8 is prepared Ifor those instances in which the port plate ltlll moves to the right, i.e the left side of the port plate 10i) moves away from the plate 132 and the right side of the port plate 1190 moves toward the face 1540i the cylinder block 94. The solid lines R1 and L1 represent the shear loss between the faces 140 and 142 and the faces 185 and 184, respectively, while the dotted lines L2 and R2 represent the 'leakage losses between the faces 185 and 184 and the faces 14) and 142, respectively. The total losses curve is the sum of the leakage and shear losses for both sides of the port plate 160 at any condition.

An example will sutlice to explain the manner in which the graph illustrates the importance of the port plate 16@ being centered. For an example assume that the port plate ltltl is 0.6X oli center toward the right. In this position the leakage losses between the port plate 11N) and the cylinder block 94 is about 0.04% as indicated by the R2 line. From the L2 line the leakage between the faces 125 10 and 134 is seen to be about 1% when the port plate 1li@ is in this position. On the other hand, the L1 line shows that the shear losses between the plate 1li-l) and the plate 132 are about 0.14% and the R1 line indicates that the shear losses between the plate ltltl and the cylinder block 94 are about 0.62%. The sum of these losses is about 1.84% as indicated on the total losses curve. Therefore, when the port plate 1li@ is .6X olf center the shear and leakage losses are about greater than when it `is centered and the desirability ofthe self-centering port plate lill) in the pump Titi is apparent.

III. The FIGURES 9-13 pump Referring now to FIGURES 9-13, a modilied swash plate pump is indicated generally by reference numeral Zilli. The pump 2d@ may be employed as a motor, but herein will be described in connection with its pump function.

As seen in FlGURE 9, the pump 2li@ includes a stationary housing or casing 232 having open ends, one of which is closed by a cover 234 suitably secured to the casing 232 by nuts and bolts or the like (not shown). Secured to the other end of the casing 252 is an outlet section 22S which cooperates with the housing 232 to hold an eccentric ring 225 in proper fixed position. Suit-able means, not shown, such as nuts and bolts may be employed to secure the outlet section 228, the eccentric ring 226 and the housing 232 together.

Rotatably supported within the section 22d and the housing 232 on anti-friction radial type ball bearings 236 and 235i is a swash plate type pump mechanism, indicated generally by reference numeral 24). An annular bearing spacer 231 prevents movement of the ball bearing assembly 236. rhe pump mechanism 24d includes a cylinder block assembly 242, a thrust member 244, a swash plate assembly 246 and a port plate 24S. The port plate 243 is rotatably supported by the bearing 236, and the thrust member 244 is rotatably supported by the bearing 238. The axis of rotation of the swash plate mechanism 240 is indicated generally by reference numeral 282.

The thrust member 244 is substantially the same as the thrust member 44 described hereinbefore. The cylinder block assembly 242 is secured to the thrust member 244 by suitable means not shown. ln this manner, the thrust member 244 and the cylinder block assembly 242 rotate together. The thrust member 244 has a thrust bearing, concave segmental spherical surface 25@ which cooperates with the swash plate assembly 246 in the same manner that the concave spherical surface Si) of the thrust member 44 cooperates with the swash plate assembly 46 of the pump 3d described hereinbefore.

The swash plate assembly 246 is similar to the swash plate assembly 4d described hereinbefore. lt includes a swash plate 256 having an integral, axially aligned shaft 25S. The free end of the shaft 25S is rotatably supported in an anti-friction roller bearing assembly 26d, which may be identical to the anti-traction roller bearing assembly ab described hereinbetore. The swash plate 256 has an annular swash face 262 concentrically positioned about an axis 264 of the swash plate assembly 246. The swash face 262 lies in a plane perpendicular to the axis 264 and faces toward the cylinder block assembly 242. Also extending toward the cylinder block assembly 242 is a cylindrical projection 245 coaxial with the axis 264 and integral with the swash plate 256. This cylindrical projection 265 is identical to the cylindrical projection d5 discussed hereinbefore and has a segmental spherical socket 266, coaxial` with the axis 264 of the swash plate assembly 24d, which opens toward the cylinder block assembly 242. As in the pump 3l) described hereinbefore, a segmental spherical ball end surface 268e of a lluid dispenser 26S lits within the socket 266, its outer periphery being in substantially fluid-tight engagement therewith to form a chamber 267. Extending axially through the dispenser 26S is 'awaits l l a passageway 269 which communicates with the chamber 267.

Also communicating with the chamber 267 is an axially extending passageway 27@ in the swash plate 256 which branches out into radially extending passageways 222 communicating with an annular groove 27d formed between annular' lands 2% and 27S on the exterior' surface of the swash plate 256. Segmental spherical surfaces 2S@ of the lands 276 and 273 deilne a segmental sphere having a diameter substantially equal to the diameter of the concave,

eginental spherical surface 25d of the thrust member Accordingly, the swash plate assembly 246 is universally tiltably associated with the thrust member 25rd.

The swash plate assembly 246 is tiltable by moving its axis 26d in a swash or tilt plane 293 (see PGURES l0 and ll). T he axis of rotation lies in this plane 223, The tilting is effected by moving the free end of the shaft 253 which is supported in the radial roller bearing 26h. The swash angle between the axis 264 of the swash plate .assembly 2126 and the axis of rotation is referred to generally by A. it will be understood that when the swash angle A is that the axis 26d of the swasn plate assembly andthe axis of rotation coincide.

The pump Zilli is provided with a guide member 224 which is similar in all respects to the guide member o 2 293 in which the swash plate assembly 24e is tilted. These cooperate with the two ilats (not shown) on the guide member 23d whereby rotation of the pinion 223 moves f the guide member 28d along the flats of the cover 23d to increase or decrease the wash angle A on either side of the axis of rotation 232. ln this manner, the swash plate assembly 24e may be tilted to control the capacity and direction of flow of the pump 26%.

The cylinder block assembly 242 includes a cylinder block 29d having a plurality of cylinders 29S therein, each cylinder 2% containing a reciprocable piston 2%, The pistons 2% have convex, spherical heads 2%.@ which cooperate with the swash face 262 of the swash plate 256. The swash face 262 normally contacts the heads 296511 otf the axes of the pistons 2% so that relative movement between the swash plate 256 and the cylinder block 294i will cause the'pistons 2% to rotate within the cylinders 29S. This minimizes uneven wear on the pistons 2% and the cylinders 29S.

The cylinders 298 have cylinder ports 3h0. The pistons 2% reciprocate during the rotation of the pump mechanism 240 at other than zero swash angle, the amount of reciprocation and, accordingly, the pump displacement, increasing with increased swash angle. Oil to be pumped enters each cylinder 298 through its respective port 300 as its associated piston 296 moves away from the port Sill) and the oil is discharged under pressure from the cylinder 293 as its associated piston 295 moves toward the port Bilt). The oil is supplied to the piston cylinders 293 through an opening 3tl2 in the housing V232 and discharged from the cylinders 293 through the cylinder ports 35d@ tothe port plate 268.

ln the pump Zilli the axis of the piston 2% and the cylinders 298 are parallel to the axis of rotation 252. lt will be understood, however, that the axes of the pistons 2% and the cylinders 298 may be in any conguration so long as their ports Sill) have a generally circular conguration.

Likewise, though the pump 2% of the present inven- `tion has been illustrated with nine pistons 2%, it will be understood that any number of pistons may be employed. It is preferable to employ an odd number of pistons.

For rotating the cylinder block assembly 242, the

thrust member 244, the swash plate assembly 246 and the port plate 243, the cylinder block 2% has integral therewith a drive shaft 204i which extends through an Aaxial aperture 2do in the outlet section 228. A seal 2li) prevents oil from leaking through the aperture 2% around 5 the shaft 204. p

An axial passageway 31S extends into the drive shaft 264. ln huid-tight engagement with the passageway 3l?,

is a holding member 320 which has an axial passageway 321 therein. Supported within the passageway 321 is a l0 spring 322 which acts upon a cylindrical positioning member 324. The cylindrical positioning member 324 is axially movable within and in fluid-tight engagement with the passageway 321. The spring 322 acts upon the inner end of the positioning member 324 to urge its other end into abutting relationship with the uid dispenser 268.

The force of the spring 322 upon 4the holding member 32d and the positioning member 324 will keep the holding member 32@ in fluid-tight engagement with the cylinder block 294 and passageway Siti.' It will be understood however that the holding member 32u may be press-fittted into the passageway 31S. The holding member 32th has at its inner end a passageway 319 connecting the passageways 31d and 321. n An axially extending passageway through the position- D ing member 324 has secured therein by a press lit or the like a iiuid transfer member 326 have a longitudinally extending groove thereon which forms with the positioning member 324 a capillary passageway 328. ln this manner o lluid may ilow from the passageway 31S through the u passageways 319, 321, 32S, 269, 276 and 272 to between the surface u andthe surfaces 23u.

As shown in FGURE 9, the outer end of the fluid transfer member 326 is spaced suciently inwardly from 35 the outer end of the positioning member 324 to assure that the capillary passageway 328 will communicate with the passageway 269 in the iluid dispenser 26u, despite small transverse movement of the iiuid dispenser 268. It will be understood from the above discussion that the AG positioning member 324 and the iluid transfer member 328 are identical to the positioning member 124 and fluid transfer member 128, respectively, of the pump 30.

Splined or keyed to the drive shaft 204 are the port plate 24S and an annular spacer 334. The spacer 33d is positioned between the port plate 245 and the cylinder block 294 and held in this abutting relationship by a nut 314 threadedly engaging the shaft 2M. The port plate 24S, the spacer 334 and the cylinder block 294 rotate at the Vsame speed as the shaft 204. The spacer 334 has a slightly larger longitudinal dimension, in the order of about .0005 inch, than a rotatable annular follower ring 24E-tl which cooperates with the eccentric ring 226 and is positioned between the port plate 248 and the cylinder block 291i. The larger longitudinal dimension of the spacer 53d promotes the self-centering feature of the follower ring 3d@ to be discussed in more detail here inafter.

The eccentric ring 226 has a longitudinally extending, circular opening 227 therethrough, the axis of which is eccentric to the axis of rotation 282. opening 227 is the annular follower ring 340 having concentric inner and outer peripheries. The outer periphery of the follower ring Edil cooperates with the periphery of the opening 227 through the ring 226 whereby the fol- 0 lower ring 340 may rotate and move axially therein.

Gn one side of the yeccentric ring 226 there is la groove 342, facing the cylinder block The groove 342 has varying dimensions depending upon the width of the eccentric ring 22e at that point. A plurality of holes 70 344 extend longitudinally through the eccentric ring 226 and communicate with the groove M2.

The port plate 248 has an annular face 345 which cooperates with the follower ring 346 and the eccentric ring 226. in the face of the port plate 24S are nine relief ports 348 which have identical cross-sections Within the circular Y to the cylinder ports 3% of the piston cylinders 293i. The relief ports 3148 are aligned with the cylinder ports 300.

In addition, the port plate243 has a plurality of passageways 35i) which communicate with the passageway 31S through an annular groove 352 in the port plate 248 and radially extending holes 354 through the drive shaft 204 (see FIGURES 9 and l2). In this manner uid may iiow from the piston cylinder 298 through the passageways 350, the annular groove 352 and the passage- Ways 354 into the passageway 31S of the drive shaft 204. Also communicating with the passageway ST8 are radially extending holes 356 which communicate with an loutlet zone 35S in the outlet section 228 r(see FIGURES 9 and 13). A wall 36u of the outlet zone 358 has holes through which the drive shaft 2M extends. The wall 35i? `and the drive shaft 204 are in fluid-tight engagement by means of seals (not shown) or the like well known in the art.

IV. Operation of the FIGURE 9-13 pump `assembly 242 and the thrust member 244 rotate in the same direction and at the same speed as the drive shaft 204. The contact of the swash face 262 of the swash plate 256 upon the pistons 296 and the force exerted by the positioning member 326` upon the uid dispensers 68 cause the swash plate assembly 246 to rotate in the same direction as these other members and at substantially the same speed. However, it is not essential that the swash plate assembly 246 rotate at the same speed as the cylinder block assembly 242 or the thrust bearing member 244. Also, the follower ring 34u will rotate in the same direction because the shear friction it has with the port plate 24S and the cylinder block 294 is` greater than the force of rictional engagement with the eccentric ring 226.

It will thus be understood that during the rotation of the cylinder block assembly 242 that the pistons 296 will be reciprocated in the same manner as the pistons 96 were `reciprocated in the pump 32. The piston cylinders 29S of those pistons 295 going through their intake stroke communicate through cylinder ports 39u with the inlet opening 302 in the housing 232 whereby oil under suicient charging pressure to force the pistons 29o into contact with the swash face 262 of the swash plate 256 enters the inlet opening 392 of the housing 232 and `passes between the eccentric ring 226 and the end of the cylinder block 294 into the piston chambers 293 via the cylinder ports 300. As the piston 296 reaches bottom dead center position, its respective port 39u is blocked olf by the follower ring 340 and will no longer communicate with the inlet 322.

As the cylinder block 242 continues to rotate the piston 296 begins its compression stroke due to its cooperation with the swash face 262 of the swash plate 256. Simultaneously therewith the cylinder port 3h0 delivered to any desired source. As the piston 29d completes its compression stroke, i.e., it reaches top dead In this manner, as the piston 29 moves toward `center position, the annular ring again blocks of cylinder port The cycle is repeated as the piston 296 begins its intake stroke and simultaneously its piston chamber 293 communicates with the inlet opening 02 in the housing Viewing FIGURES l0 and l1, the manner in which the iluid flows into the piston cylinders 298 during the intake stroke of the piston 2% and flows through the port plate 243, the passageway 3th and the outlet zone 358 during the compression stroke of the piston 29o will be apparent. The arrows in FIGURES l0 and 11 indicate the flow paths of the oil. Since the annula follower ring 34th is eccentrically mounted in the ring 226, the ports Sil@ of the piston chambers 293 will be either blocked by the ring 340, communicate with the interior of the ring 340 or communicate with the exterior of the ring 344) as the cylinder block 294 rotates. The ports Sil@ are blocked by the ring 34u when their respective pistons 296 are at top dead center position or bottom dead center position. As seen in FIGURE ll, one of the ports 30) is blocked by the follower ring 34) as its associated piston 296 is at top dead y center position. On the other hand, the cylinder ports 326 communicate with the exterior of the follower ring 34u as their respective pistons 296 are going through their intake stroke and oil from the inlet 322 ows between the `cylinder block 294 and the eccentric ring 226 through sageways 356 into the outlet zone 35S where it is delivered to any desireddestination.

It will be understood that if the swash angle A is decreased, the capacity of the pump 20u is decreased as the pistons 296 go through a shorter intake and compression stroke. Therefore, it will be understood that when the swash angle A is zero degrees, no pumping action is effected by the pump Zitti.

If the shaft 224i is rotated in the opposite direction, the flow of fluid in the pump Ztl@ is reversed. That is,the oil enters the Zone 353 and is `discharged under pressure through the opening 392.

Likewise, as in the pump 3d, the oil flow of the pump 2th) may be reversed by actuation of the pinion 283 to change the swash angle A so that it is on the opposite side of the axis of rotation 282.

Thrust, of course, is created during the operation of the pump 26u. As in the pump 3l?, and in accordance with this invention, the thrust is transmitted from the pistons 296 to the swash plate assembly 246, but instead of being transmitted from the swash plate assembly 246 to the casing through a thrust bearing, the thrust force exerted against the thrust member E44 is carried baci; to the cylinder block FurthermoreJ by this arrangement the need for a universal joint has been eliminated. In the pump 294i the surfaces 28@ of the lands 276 and 27E cooperate with the concave surface 25d of the thrust member 244 in exactly the same manner that the surfaces Sti of the lands 76 and itl cooperate with the concave surface Sil of the thrust member 44 in the pump Sii( The lonly difference is that the pressurized oil is supplied be.- `tween these cooperating surfaces from the passageway 323. The fluid iiows through the passageway i9 of the holding member 32@ into the chamber 322 from which it `iiows through the capillary passageway 323 and the pas- 1sagevvays 269, 270 and 272 to the annular groove 274 on the periphery of the swash plate 256. Thus, the swash plate 256 is automatically separated from the thrust member 244 by an oil film of predetermined thickness in the snee-,ire

l5 same manner described hereinbefore in detail with respect to the pump 3?.

To reduce shear losses between the follower ring Edil and the port pate 2413 and the cylinder block 294, the port plate 248 has relief ports 34S which are the same size as the cylinder ports Sil@ and are aligned therewith. Likewise the cylinder block 2.94 has a relief port 357i opposite each passageway 35u and axially aligned therewith. The relief ports 351 have the same cross-sectional area as the passageways 35d in the port plate 24S. ln this manner, where the follower ring 3d@ extends between the passageway $5@ and the relief port 351 both sides of the follower ring Sridhave the same area exposed to the pressure of the oil in the passageway 35d. Likewise, the pressure exerted through the ports Sil@ upon one side, the follower ring Edi) will be counterbalanced by the oil under the same pressure which flows through the holes 34d and the eccentric ring 226 to the relief ports 343. Where the ring 340 prevents communication between the port 3b@ and the inlet StlZ, there is direct communication between the port 3M and the relief port 343. Thus, any pressure exerted through oil at the port 3Q@ will be counterbalanced on the other side of the ring 34) by oil in the relief port 343 at the same pressure and acting upon the same crosssectional area on the other side or" the ring Mtl. In this manner the ring Sdi) is maintained in a substantially balanced position between the port plate 248 and the cylinder block 294, thus reducing shear losses between these parts.

l/.VT/ze embodiment of FIGURES 14 and l5 Referring now to FIGURES 14 and l5, there is illus- Y trated a modified form of the present invention which may be employed in the pump or motor 3i) or 260. ln this embodiment the pistons are cooperatively secured to the swash plate assembly whereby the relative movement between the cylinder block assembly and the swash plate assembly causes the pistons to move through their intake stroke. This is contrasted with the pumps 30 and Ztl@ wherein the pistons are maintained in contact with the swash plate assembly during their intake stroke by the charging pressure of the inlet oil.

As seen in FIGURE 14, the pump 4% includes a stationary housing or casing 462 rotatably supporting therein a cylinder block assembly 4M, a thrust member d66 and a swash plate assembly 4Gb. The thrust member tile is secured to the cylinder block assembly 464i, the thrust member 4% being substantially identical to the thrust member i4 of the pump 3?, and the thrust member 244- of the pump Zilli?. The swash plate assembly idg is substantially identical to the swash plate assembly 46 of the pump 3i? and the swash plate assembly 246 of the pump Edil and cooperates with a concave surface llltl of the thrust member 4% in the same manner described hereinbefore with respect to the pumps Si) and EN?.

The cylinder block assembly 464 is similar to the cylinder block assemblies described hereinbefore, with the exception that its pistons l1-.2 have a-modied construction. Furthermore, a positioning member 414 is housed directly within the cylinder block 404 to cooperate with the fluid dispenser ed.

The pistons 412 are hollow and have convex segmental spherical heads 416. Guide members 418 having concave segmental spherical sockets lisa are connected to the pistons 412 by internal ball joints d2@ secured in place by a snap ring 422. Each ball joint 2-2li has an axially extending hole 424 which connects the interior of the piston 4112 with a flat surface 425 of the spherical guide member 41S, which surface 426 cooperates with the tace of the swash plate assembly 468. A passageway 42S in the spherical guide member llallows oil to pass back to the point where the ball joint 420 cooperates with the piston 412.'

A disc 43th having radially extending arms 432 holds the sperical guide members di@ in position. The fluid dispenser d8 cooperates with a segmental spherical socket 434 in the disc 430. The disc 43@ has a cylindrical projection 436 which is in Huid-tight engagement with an axial passageway 4.38 in the swash plate assembly 40S. A passageway 44@ extends from a cavity 435 formed bythe iluid dispenser 63 and the socket 434 to the end of the projection 43d. In this manner fluid flowing through the positioning member 414 and the fluid dispenser 68 may ow through the passageway 44) into the radial passageways '72 between the surface 41u of the thrust member 406 and the exterior surfaces of the swash plate assembly fltl. lt will be understood that the balance between the thrust force exerted by the pump 4th@ will be effected between the swash plate assembly 463 and the thrust member 465 in the same manner described hereinbefore with respect to the pump or motor 3) and Zlltl.

During operation of the pump 460 the relative movement of the swash plate assembly 463 away from the cylinder block 494 will cause the spherical guide members it to move away from the cylinder block 494 and,

through the ball joints 42d, move the pistons 416 for their intake stroke. As the pistons 412 go through their pressure stroke, oil will ow through the passageway 424 in the ball joint 426 and flow between the face 426 of the guide member 41S and the cooperating face of the swash plate assembly 4&8. In this manner a predetermined oil lm between the guide member 413 and the swash plate assembly 498 will be assured. Thus, if there is any relative rotation between the disc 432, and therefore the guide members 418, and the swash plate assembly 468, the shear losses between the guide members 418 and the swash plate assembly 40S will be minimized. Likewise oil may iiow through the passageway 428 between the piston head 416 and the guide member 418 to prevent any shear losses which may occur between these members.

It will be understood that with respect to the other operational features of the pump 40) that they are identical to the pump 34B or the pump 200, depending upon the particular type of porting arrangement provided.

VI. Control system Referring now to FIGURES 16-19, there is illustrated a control system adapted to change the swash angle A between an axis of rotation 500 of a pump like the pumps 3i), 2d@ and 400 and an axis 502 of a swash plate assembly 5614- employed in such a pump. lt will be understood Y that the swash plate assembly 504 may be identical to any one of the swash plate assemblies described hereinbetore. This control system is fluid pressure actuated.

As seen in FIGURES 16 and 17 a free end of a shaft 596 of the swash plate assembly 5 4 is supported in an anti-friction radial ball bearing 56S. The ball bearing assembly 598 is suitably secured, by means of a press t or the like, within a non-rotatable guide member 51) having an external rack 512 thereon which cooperates with a pinion 514. The cover 516 of the pump has two opposing parallel internal guide tlats 518 which are parallel to the tilt or swash plane. These cooperate with two complementary llats 524i on the guide member 516 whereby rotation of the pinion 514 moves the guide member Siti parallel to the guide ats 524D to increase or decrease the swash angle A on either side of the axis of rotation 500. To this'point the arrangement is'identical with that described hereinbefore with respect to the pump 3i? and the pump Zltl.

The pinion Sie is mounted upon a rotatable shaft 522 supported by bushings 524 and 525 secured to the cover Sie. One end of the shaft 522 extends into a servo control assembly indicated generally by reference numeral S26. The shaft 522 has a passageway 528 through which Yfluid under pressure from a suitable source (not shown) is directed to the servo control assembly'526 to regulate the movement of the pinion 514 in a manner more apparent hereinafter.

The servo control assembly 526 includes a stationary a', los, i 7a housing 527 secured to the cover 51o. knob 53h having a shaft 532 with an annular flange 53d is rotatably mounted upon the housing 527. Secured to the flange 534 is an annular` ring 53o. As will be more apparent hereinafter, rotation of the knob 53@ and the ring 53o causes the shaft 522 and the pinion 514 to rotate the same number of degrees in the same direction, thereby tilting the swash plate assembly 50d as desired.

The housing 527 has two radially, inwardly extending walls 53S and dat) (see FGURE i9) which are in fluidtight engagement with an annular section 542 of a pressure responsive means, such as rotary piston `member 541i, keyed to the shaft 522. Together with the cover 5M and a wall 529, the walls 538 and Edil form a fluid-tight chamber 54u within the housing 527. The rotary piston meinber 544 is in fluid-tight engagement with the walls of the chamber S46, but is movable therein in a manner more apparent hereinafter.

Extending radially from the passageway 52h in the shaft 522 is a passageway 55d which communicates with a short groove 552 on the periphery of the shaft 522. The ring 536 has a land 55d which has the'same cross-sectional configuration as the groove 55?., but has slightly larger dimensions. On opposite sides of the land 5554 are grooves and 558 in the ring 53d. Communicating with the grooves 556 and 553 are passageways 5d@ and 562, respectively, in the shaft 522, These passageways 5d@ and 562 also communicate with the chamber on opposite sides of the rotary piston member 544. Grooves 5nd and 5de on the sides of the passageway/s Sti@ and 562 extend along the periphery of the shaft 522 to carry displaced fluid from the chamber Sri/5 to any desired destination, eg., to the area in the cover 5to. The groove 55o has substantially the same dimensions as the land 56S between the grooves 564 and 552. Likewise the groove 55S has substantially the same dimensions as the land 57d between the grooves 552 and 566.

To change the swash angle A between the axis 5M of the swash plate assembly 5M and the axis 5%, the knob 530 is rotated through an arc corresponding to the number of degrees in which the pinion 514 is desired to be rotated. The ring 536 will likewise be rotated the same number of degrees causing the land 554 to be disaligned from the groove 552. if, for instance, the knob 53d is rotated in a clockwise direction when viewing FIGURES 18 and` 19 this will cause the passageway 55u to communicate with the groove 556 whereby fluid under pressure passes through the groove 55o and the passageway dei) to the pressure chamber 546. The pressure of the rluid entering the pressure chamber 54o from the passageway Soll causes the rotary piston member 544 to move in a clockwise direction in the chamber 545. Fluid is displaced from the chamber 546 by such movement of the member 54d and it flows through the passageway 562, the groove 558 and the groove 566 to the cover 5o or any other suitable source. As the rotary piston member 544 rotates in a clockwise direction, the shaft 522 will also be rotated in a clockwise direction until the groove 5.52 again becomes aligned with the land 55d. When this occurs the dow of lluid to the pressure chamber 546 will be cut oit or terminated. This occurs when the shaft 522 has been rotated through exactly the same number of degrees as the knob 530.

Likewise, if it is desired to rotate the shaft 522 in a` counterclockwise direction, the knob 55d is rotated in a counterclockwise direction. This causes the passageway 550 to pass pressurized iiuid through the groove 55d and `the passageway 562 to the iluid pressure chamber Edd.

`same number of degrees.

lt will be understood that the section headings in this application are merely a matter of convenience and are not limitations upon the present invention.

While several embodiments described herein are at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modications and improvements as fall withinV the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

ll. A swash plate huid device comprising a casing having rotatably mounted therein a cylinder block assembly, a rotatable swash plate assembly and a rotatable thrust member, said cylinder block assembly having a plurality of pistons reciprocably mounted therein, said swash plate assembly cooperating with said pistons for reciprocating said pistons, said thrust member having a` concave, segmental spherical surface which cooperates with a convex spherical surface of said swash plate assembly, the thrust load of said piston against said swash plate assembly being transmitted from said surface of said swash plate assembly to said surface of said thrust member, means connecting said thrust member and said cylinder block assembly whereby said thrust load is transmitted directly from said thrust member to said cylinder block assembly.

2. in a swash plate fluid device including a casing having rotatably mounted therein a cylinder block assembly and a swash plate assembly, said cylinder block assembly having a plurality of pistons reciprocally mounted therein and said swash plate assembly cooperating with said pistons for reciprocating said pistons, a port plate mounted within said casing and axially movable therein, said port plate positioned between an end of said cylinder block assembly and a plate rotating with said cylinder block assembly, said port plate allowing oil to enter said cylinder block assembly and receiving oil discharged from said cylinder block assembly and automatically centering itself between said plate and said cylinder block assembly.

3. ln a swash plate fluid device comprising a casing` having rotatably mounted therein a cylinder block assembly and a swash plate assembly, said `cylinder block assembly having a plurality of piston chambers, each having a cylinder port and a reciprocal piston, said cylinder port communicating with an end of said cylinder block assembly remote from said swash plate assembly, said swash plate assembly cooperating with said pistons for reciprocating said pistons in said piston chambers, a port plate adjacent said end of said cylinder block assembly remote from said swash plate assembly, said port plate l distributing oil to said piston chambers and receivingoil discharged from said pistou chambers, said port plate being mounted within said casing and axially movable therein between said end of said cylinder block assembly and a plate rotatable with said cylinder block assembly, said plate having relief ports therein adjacent said port plate, said relief ports having cross-sectional areas substantially the same as the cross-sectional areas `of said cylinder ports, means for transmitting oil from said port plate to said relief ports whereby said port palte is automatically centered between said rotating plate and said cylinder block assembly.

a. ln the duid device of claim 3 wherein said port plate has symmetrically disposed kidney ports in opposite half sections/of said port plate, each of said kidney ports cornrriunica'ting with a channel which communicates with the exterior of said casing, whereby oil enters said device through one of said channels and is discharged from said device through said other channel, each of said channels having a capillary-type passageway leading therefrom communicating with a face of said port plate remote from said cylinder block assembly and adjacent said rotating plate.

5. In the fluid device of claim 3 wherein a spacer means maintains said plate and said cylinder block assembly apart a'distance slightly larger than the longitudinal dimension of said port plate.

' 6. A swash plate fluid device comprising a casing having rotatably mounted therein a cylinder block assembly, a swash plate'means and a thrust member, said cylinder block assembly being non-rotatably mounted upona rotatable shaft extending into said casing, said cylinder block assembly having a plurality of piston chambers therein,`each of said piston chambers having a reciprocal piston therein, said swash plate means cooperating with said pistons for reciprocating said pistons, each of said piston chambers having a cylinder port communicating with an end of said cylinder block assembly remote from said swash plate assembly, a rotating plate ixedly mounted on said shaft, a non-rotatable port plate mounted within said casing between said remote end of said cylinder blo-ck assembly and said rotating plate, said nonrotatable port plate being free to move axially between said 'cylinder block assembly and said rotating plate, said port plate having two channels therein both of which communicate with the exterior of said casing whereby oil enters said piston chambers through one of said channelsv and isrdischarged from said piston chambers through said other channel.

` 7, The fluid device of claim 6 wherein said port plate has a first and second side, each channel in said port plate having a kidney port opening in said first side toward said cylinder ports, said kidney ports being symmetrically disposed in` opposite half-sections of said rst side of said port plate, each'channel having a capillary-type passagewayv extending therefrom which communicates with said second side of said port plate which is adjacent said rotating plate whereby said port plate automatically is centered between said cylinder block assembly and said rotating plate. Y

8. The fluid devicel of claim 7 wherein a face of said port plate adjacent said second side of said port plate has relief ports therein being axially aligned with and having substantially the samecross-sectional dimensions as said cylinder ports, said second side of said port plate having two kidney-shaped vrelief ports therein axially aligned with and having substantially the same cross-sectional dimensions as said kidney ports, said capillary-type passageways from said channels communicating with said kidneyshapedrelief ports.

9. The fluid device of claim 6 wherein said thrust member has a concave, segmental spherical surface which cooperates with a convex, segmental Spherical surface of said swash plate assembly, means connecting said thrust member and said cylinder block assembly whereby a thrust load against said swash plate assembly is transmitted to said thrust bearing member and back to said cylinder block assembly and means for providing a film of predetermined thickness of oil between said surface of said swash plate assembly and said surface of said thrust member.

10. The fluid device of claim 9 wherein said means for providing a film of pre-determined thickness of oil includes a passageway communicating with the channel in saidV port plate receiving the oil discharged from said pistonl chambers, said passageway delivering oil from said channel to between said surface of said swash plate assembly and said surface of said thrust member and having therein a capillary passage which causes a pressure drop on the oil flowing from said channel to between said surface of said swash plate assembly and said surface of said thrust member.

il. A swash plate fluid device comprising a casing having rotatably mounted therein a cylinder block assembly, a swash plate assembly and a thrust member, said cylinder block assembly having a plurality of pistons reciprocally mounted therein, said swash plate assembly cooperating with ysaid pistons for reciprocating said pistons, said thrust member having a concave, segmental spherical surface which cooperates with a convex segmental spherical surface of said swash plate assembly, the thrust load of said piston against said swash plate assembly being transmitted from said surface of said swash plate assembly to said surface of said thrust member, means connecting said thrust member and said cylinder block assembly whereby a thrust load against said swash plate assembly is transmitted to said thrust member and back to said cylinder block, and means to provide an oil film of predetermined thickness between said surface of said swash plate assembly and said surface of said thrust member.

i2. A swash plate pump comprising a casing having rotatably mounted therein a cylinder block assembly, a swash pla-te assembly and a thrust bearing member, said cylinder block assembly having a plurality of pistons reciprocallly mounted the-rein, said swash plate assembly cooperating with said pistons for reciprocating said pistons, said thrust bearing member having a concave, partially spherical surface which cooperates with a convex, partially spherical face of said swash plate assembly, means connecting said thrust bearing member and said cylinder block assembly whereby a thrust load against said swash plate assembly is transmitted through said thrust bearing member to said cylinder block assembly, means for providing an oil film of pre-determined thickness between said faces of said swash pla-te assembly and said surface of said thrust bearing member, said means including a passageway communicating with a port plate which receives oil discharged from said cylinder block assembly, said passageway delivering oil from said port plate between said face of said swash plate assembly and said surface of said thrust bearing member, said oil flowing through a restricted passage whereby the pressure of said oil is reduced as it flows therethrough.

13. yIn the iiuid device of claim 12 said means for providing an oil lm including a iiuid dispenser cooperatively engaging said swash plate assembly and a spring-biased positioning member in said passageway abutting said iluid dispenser and holding it in cooperative engagement with said swash plate assembly, said positioning member having said restricted passage therein whereby said oil travels through said restricted passage and said fluid dispenser as it Itravels .to between said surfaces of said thrust member and said swash plate assembly.

i4. in the iiuiddevice of claim 13 wherein said swash plate assembly has a segmental spherical socket opening toward said cylinder block assembly, said fluid dispenser being a segmental, spherical member extending into said socket and being held therein by said positioning member, said fluid dispenser having a passageway therein through which said oil passes.

l5. A swash plate fluid device comprising a casing having rotatably mounted therein a cylinder block assembly and a swash plate assembly, said cylinder block assembly having a plurality of piston chambers each having a piston reciprocally mounted therein, said piston chambers communicating through cylinder ports with an end of said cylinder block assembly remote from said swash plate assembly, said swash plate assembly cooperating with said pistons for reciprocating said pistons, an eccentric ring ixedly mounted within said casing and supporting a rotatable annular follower ring positioned adjacent said cylinder ports, said annular follower ring being supported in said eccentric ring whereby lits axis is eccentric to a longitudinal axis of said cylinder block assembly, a port plate mounted within said casing and rotating with said cylinder block assembly, whereby fluid enters said cylinder port vand its piston chamber when said cylinder port is on one side lof said follower ring and liuid is discharged from .said piston chamber when said cylinder port is on the other side of said follower ring, said eccentric ring having a plurality of holes therethrough by which oil may liow between said annular follower ring and said port plate, said port having a face adjacent said follower ring with relief ports, each relief port being axially aligned with a port in said cylinder block assembly and having substantially the same cross-sectional dimensions as the ports with which it is aligned whereby said follower ring is maintained substantially equidistant between said port plate and said cylinder block assembly.

i6. The swash plate fluid device of claim 15 wherein said cylinder block assembly has a shaft connected thereto which extends axially from said casing, said port plate being non-rotatably secured to said shaft, said casing having an outlet section therein, said outlet section coinmunicating with an oil passageway in said shaft, said port plate hav-ing a passageway therein whereby oil is discharged from said piston chamber through said ports, passes through said passageway in said port plate and said oil passageway in said shaft to said outlet section in said casing.

References Cited by the Examiner UNiTED STATES PATENTS 9/09 l/34 8/34 5/41 4/42l 7/42 7/42 6/47 1l/52 4/54- ll/55 7/58 2/58 12/53 2/59 12/60 4/61 6/61 6/62 Macornber 1013--162 Benedek 103-162 Walker et al. 103--162 Doe 163-162 Wahlmark 103--173 Zimmermann 1GB-162 Neuland 103-162 Neuland 103--162 Born 10S-162 Ferris 103-162 Wahlniark 103-173 X Wennberg 103--162 Gondek 10B-1612 Bauer 10k-1612 Thoma 10S-162 Wiggerman 10S-162 Gille 121--38 Rumsey 121-38 Adams 121-38 RGBERT WALKER, Primary Examiner. LAURENCE V. EFNER, Examiner. 

1. A SWASH PLATE FLUID DEVICE COMPRISING A CASING HAVING ROTATABLY MOUNTED THEREIN A CYLINDER BLOCK ASSEMBLY, A ROTATABLE SWASH PLATE ASSEMBLY AND A ROTATABLY THRUST MEMBER, SAID CYLINDER BLOCK ASSEMBLY HAVING A PLURALITY OF PISTONS RECIPROCABLY MOUNTED THEREIN, SAID SWASH PLATE ASSEMBLY COOPERATING WITH SAID PISTONS FOR RECIPROCATING SAID PISTONS, SAID THRUST MEMBER HAVING A CONCAVE, SEGMENTAL SPHERICAL SURFACE WHICH COOPERATES WITH A CONVEX SPHERICAL SURFACE OF SAID SWASH PLATE ASSEMBLY, THE THRUST LOAD OF SAID PISTON AGAINST SAID SWASH PLATE ASSEMBLY BEING TRANSMITTED FROM SAID SURFACE OF SAID SWASH PLATE ASSEMBLY TO SAID SURFACE OF SAID THRUST MEMBER, MEANS CONNECTING SAID THRUST MEMBER AND SAID CYLINDER BLOCK ASSEMBLY WHEREBY SAID THRUST LOAD IS TRANSMITTED DIRECTLY FROM SAID THRUST MEMBER TO SAID CYLINDER BLOCK ASSEMBLY. 